I purchased a Sako 75 SS in 7mm recently. I purchased 150 pieces of new win brass, all the same lot#, weighed them and sorted out all +/- 1.5%, straightened out the mouth's, did the flashholes and primer pockets, and loaded up test loads with this brass for RL 19, RL 22, IMR 4831, and IMR 4350 at 3 loads each 1.0 gr apart up to the book max. I also purchased a brand new Zeiss Conquest 6.5x-20x 50mm and mounted it myself using Burris Rings that I received with the gun.
Of my test powders, using 160 gr Accubonds, I had 4 loads all under 1.0" so I loaded up enough for 3 more test groups for each of these. These included RL 22@ 61.0 gr, IMR firstname.lastname@example.org
gr, and 59.5 and 60.5 gr's of RL19. In the end I chose the RL19 as in 8 test groups with both poweder charges I had groups from .35 to .70 ave .52.
So I next loaded up more of the 60.5 gr's to further test, with no variations to the load or gun except that I had run out fo the Nosler's and had to purchase a new lot. The cold barrel foul shots went into just under an inch, then the first group was again at .5". The next groups started with two less than .5", but the third was over 1.5" away. I thought it might be a flyer, so I shot a fourth, again 1.5" in a diff direction. Two more groups provided 1.5 and 2.25" groups.
After some advice here I checked the action screws, which actually turned 1/3-1/2 turn fairly easily, then I checked the scopre mounts and ring screws, so I tightened them slightly. This provided no benefit. Then I switched scopes to a spare Bushell Elite 3200 3x9, to no benefit. I bought a new box of Accubonds, just in case it was a bad batch, but no help. I had one group at .75", but all others were between 1.5" and 2.5".
My groups typically have two of three that are good and a third that doesn't seem to have a typical pattern and is usually .75-2.0" away. It isn't necessarily vertical or horizontal. Before they started to open up, two of three on all 8 first groups mentioned had two in the same hole with the third .3-.7 inches away.
I'm new to this and was very excited to get such consistent loads, and now I'm quite depressed. It seems like something went wrong all of a sudden. I dont' think it's me, as I can take my kids gun that shoots consistently under an inch and consistently shoot under an inch with it. I can understand the occasional flyer, but now one out of three.
Should I take the gun to a smith for a bedding job. The barrel seems floated with no resistance on a dollar bill and I can't easily push the stock to meet the barrel.
Additionally I thoroghly cleaned the barrel before each use, fouled with 3-4 shots, allowed about two minutes after the first shot, about 3-4 after the second and at least 5 minutes in the shade with the action open between groups.
Please help with some advice?